1. Technical Field of the Invention
The present invention relates to a spread spectrum communication system suited for a mobile communication system such as a cellular phone system, and in particular to a spread spectrum communication system of the direct sequence type that spreads and despreads a signal to be transmitted, using a spread code such as a pseudo noise sequence (PN sequence.)
2. Related Art
In a spread spectrum mobile communication system of the direct sequence type, a receiver receives a plurality of signals from a transmitter via a plurality of different paths existing between the receiver and the transmitter. The receiver also acquires and tracks several better signals among the received signals, thus combining the tracked signals to demodulate the combined signal.
However, during an intermittent transmission in which the transmission power of each of the plurality of signals is reduced to save power consumption, there may be a plurality of noises larger than the desired signals, so the receiver may acquire and track the noises instead of the desired signals. Consequently, after resuming the transmission after a pause in the intermittent transmission, the receiver cannot demodulate the desired signals until the receiver newly acquires and tracks the desired signals instead of the noises.